You are right, those are fairly easy to home-brew using the technique you described. The one I use in the video is purchased though, it is an RFA-4059A that I got from those guys: www.rfparts.com/signal-samplers/rfa4059a.html It came with a nice calibration curve and you can coarsely adjust the coupling because the "tap" slides back and forth before it is fastened, but at the end of the day it's just a glorified version of what you described.
Thank you for taking the time to put this video together. I'd like to make an observation and it is certainly was not intended to be insulting. Get to the point! Well over 15 minutes in and you still hadn't discussed setting up and actually measuring the desense.
Hello Daniel. Yeah I should have showed that. I don't even remember how much it was but it was so bad that it was clear something had to be done about it. As for the testing without ISO-TEE, I would be interested in learning more about that method if you know anything. I only have the manual which specifically calls for an ISO-TEE.
+MrCircuitMatt Normally I would measure SINAD on the AF off the receiver, then adjust the signal generator to a level through the ISO-TEE where I have 12dB SINAD on the receiver without transmitting. Then I fire op the transmitter and then adjusting the signal generator level to 12dB SINAD reading. The level difference between the to measurements is your desensitization level :) Sorry. One port duplex measurement is only an option on the R2600 series service monitor, not on the R2400 series.. My bad. But I have an R2001D/HS service monitor I normally use when I have on-site jobs, so I know the trouble about using an ISO-TEE.. I usually use my Bird 4431 wattmeter with variable RF tap instead off the ISO-TEE.. On the workbench I have the Schlumberger Stabilock 4032, the Stabilock 4040 and the Motorola R2600 service monitor. They all offer one port duplex measurement. I have just finished 2 UHF repeaters for rental :) What type of Procom filter are you using ? 73 de. OZ99DW
+Daniel Wahl Yes I did a similar test as well. I didn't show the whole thing because I think that a video blog is not the proper way to teach people how to build repeaters. This is more of a 'look how I did this, you might find it interesting or have comments' thing and I always enjoy it when it leads to discussions such as that one. Our group does have a service monitor with duplex measurement capabilities -- a R&S CMT54 if memory serves. This is not in my home lab though and I originally wanted to get as much as possible done at my place. This is why I did the two videos on the Bessel-Null method, and only then did this guy drop his old monitor in my driveway. That's why things might look a bit convoluted but I always enjoy experimenting and seeing what can be achieved with amateur-means. The Procom filters are BRBP70/6. I would have made a different choice there but that decision was made by my predecessor in the group and I can't overturn that. Good luck with your repeaters and 73 Matt
Super video :) I'm sorry you don't show how many dB desensing appearing on your repeater set up before retuning the filter. What type of filters are you using ? I'm pretty sure that its possible to use the Motorola R2400 service monitor without the ISO-TEE to do this test. 73 de OZ99DW
So typically, the ISO-T would be inline between the duplexer’s antenna port and the dummy load. Also technically, you’d use 12 dB SINAD (or 20 dB quieting) as a reference for comparing your desense.
Thank you so much for such an excellent video. You make this all very easy to understand.
Thanks! Let me know if you have any particular questions.
Did you make your ISO-TEE or is this one you purchased? I have seen and I was even given one where the center pin was simply removed.
You are right, those are fairly easy to home-brew using the technique
you described. The one I use in the video is purchased though, it is an
RFA-4059A that I got from those guys:
www.rfparts.com/signal-samplers/rfa4059a.html
It came with a nice calibration curve and you can coarsely adjust the
coupling because the "tap" slides back and forth before it is fastened,
but at the end of the day it's just a glorified version of what you
described.
So, how to fix this? I am having this issue with my GMRS repeater
Usually it is a matter of improving isolation (or reducing output power)... what duplexer do you have? How much isolation does it have?
Thank you for taking the time to put this video together. I'd like to make an observation and it is certainly was not intended to be insulting. Get to the point! Well over 15 minutes in and you still hadn't discussed setting up and actually measuring the desense.
Hello Daniel. Yeah I should have showed that. I don't even remember how much it was but it was so bad that it was clear something had to be done about it. As for the testing without ISO-TEE, I would be interested in learning more about that method if you know anything. I only have the manual which specifically calls for an ISO-TEE.
+MrCircuitMatt
Normally I would measure SINAD on the AF off the receiver, then adjust
the signal generator to a level through the ISO-TEE where I have 12dB
SINAD on the receiver without transmitting.
Then I fire op the transmitter and then adjusting the signal generator level to 12dB SINAD reading.
The level difference between the to measurements is your desensitization level :)
Sorry.
One port duplex measurement is only an option on the R2600 series service monitor, not on the R2400 series.. My bad.
But I have an R2001D/HS service monitor I normally use when I have on-site jobs, so I know the trouble about using an ISO-TEE.. I usually use my Bird 4431 wattmeter with variable RF tap instead off the ISO-TEE..
On the workbench I have the Schlumberger Stabilock 4032, the Stabilock 4040 and the Motorola R2600 service monitor. They all offer one port duplex measurement.
I have just finished 2 UHF repeaters for rental :)
What type of Procom filter are you using ?
73 de.
OZ99DW
+Daniel Wahl Yes I did a similar test as well. I didn't show the whole thing because I think that a video blog is not the proper way to teach people how to build repeaters. This is more of a 'look how I did this, you might find it interesting or have comments' thing and I always enjoy it when it leads to discussions such as that one.
Our group does have a service monitor with duplex measurement capabilities -- a R&S CMT54 if memory serves. This is not in my home lab though and I originally wanted to get as much as possible done at my place. This is why I did the two videos on the Bessel-Null method, and only then did this guy drop his old monitor in my driveway. That's why things might look a bit convoluted but I always enjoy experimenting and seeing what can be achieved with amateur-means.
The Procom filters are BRBP70/6. I would have made a different choice there but that decision was made by my predecessor in the group and I can't overturn that.
Good luck with your repeaters and 73
Matt
Super video :)
I'm sorry you don't show how many dB desensing appearing on your repeater set up before retuning the filter.
What type of filters are you using ?
I'm pretty sure that its possible to use the Motorola R2400 service monitor without the ISO-TEE to do this test.
73 de
OZ99DW
Hello Daniel. is it possible that you do an extensive review of your motorola r2200?
I am very interested in it.
thanks in advance
So typically, the ISO-T would be inline between the duplexer’s antenna port and the dummy load. Also technically, you’d use 12 dB SINAD (or 20 dB quieting) as a reference for comparing your desense.